Synchronization of multiple media sources such as a motion picture photographic image and sound (audio) information in a final motion picture print film, i.e., the film that is shown in movie theaters, is a problem which the motion picture production industry has faced for many decades. The techniques required for recording photographic images on movie film and those by which sound is recorded on a suitable sound recording medium are quite different. Therefore, it has been common since the early days of sound films to employ two independent pieces of equipment for recording image and audio information. In the early days, images were invariably recorded as a sequence of frames on a continuous strip of photographic film, while audio was recorded as a microscopic wavy groove in either a wax cylinder or a wax disk. Some audio was recorded on the set, but much audio was recorded or re-recorded or dubbed while observing a screening of the film. Synchronization of a projected picture with corresponding audio recorded in a separate medium was quite crude. Picture and audio would be started at a reference point established at the program. The speed of one or the other would be manually adjusted when loss of synchronization was observed. However, such techniques provide very poor synchronization.
In modern studios, images may be recorded on film in a variety of formats. Audio is likely to be recorded on magnetic recording tape called a sound tape, also in a variety of formats. Whenever multiple tracks of source material are used to create a final production or composition, synchronization of one or more images with one or more tracks of audio may be required. The use of a customary slate at the beginning of each take of a scene helps facilitate synchronization of audio recorded on the set with picture recorded on the set. The slate produces a sharp and distinct sound on the audio recording, simultaneous with an identifiable visual event, such as a bar hitting the top of the board. Additionally, during recording, the camera and the audio recording equipment may be mechanically or electrically synchronized, so that corresponding lengths of film and audio media are used. Consequently, to synchronize these source media for editing or viewing requires that the sound of the slate in the audio track be aligned with the image of the bar hitting the top of the board. Then the two media may be mechanically or electrically locked together for playback or editing.
For greater flexibility, including the use of multiple sound tracks recorded in separate media either on the set or off the set, timecodes have been developed for aiding in the establishment and maintenance of synchronization in the circumstances such as described above. One type of commonly used timecode is that developed by the Society for Motion Picture and Television Engineers (SMPTE), which may be imprinted in an unused margin of the film or audio media during filming so as to indicate an absolute time reference for each frame of film. The imprinting of the SMPTE timecodes may be human readable, e.g., as numbers in the margin of the film, or may be machine readable, e.g. as bar codes in the margin of the film. Another time reference used on film media is the Eastman Kodak KEYKODE number. Among other things, the KEYKODE number acts as a roll and frame counter, by which any frame of a production may be absolutely identified. KEYKODES are recorded in the form of a latent image of the code data on film stock at the time of manufacture, after emulsion coating of the film base, in the film margin.
Synchronization during playback of multiple media sources may be achieved as follows. First, all the media are aligned manually to a starting point.
During playback, timecodes may then be read off all of the media to be synchronized. The playback speeds of the media are then adjusted so as to cause the timecodes read off the media to coincide throughout the playback. Such systems employ standard feedback techniques to cause the playback speeds of all the media but one to follow the playback speed of the one.
To eliminate the need for real time synchronization of images and sound during viewing of a motion picture, motion picture print films commonly employ optical soundtracks along at least one edge of the film, which sound tracks are already synchronized with the images. During projection of the motion picture images, a light source illuminates the soundtrack and a photosensor senses the light passing through and modulated by the soundtrack to produce an audio signal that is sent to amplifiers of the theater sound system. The most common optical soundtracks presently in use are analog soundtracks of the "variable area" type wherein signals are recorded in the form of a varying ratio of opaque to relatively clear area along the soundtrack. Digital soundtracks for motion picture films have been more recently introduced, wherein sound information is recorded in a digital format, e.g. comprising small data bit patterns on the film, typically between perforations of the motion picture film (e.g., Dolby.TM. Digital Stereo soundtracks) or along the film edge (e.g., Sony.TM. Dynamic Digital Sound soundtracks). U.S. Pat. Nos. 4,600,280 and 4,461,552, e.g., disclose methods in which digital audio is photographically recorded on motion picture film.
In order to optimize the visual quality of the motion picture image as well as the sound quality of the soundtrack recorded on a motion picture print film, the motion picture and soundtrack are first typically captured or recorded on separate photosensitive films as negative images, and the resulting negatives are then printed in synchronization on a motion picture print film to form positive images. Optical soundtrack negatives are typically best recorded with high contrast, relatively slow speed films (e.g., Eastman Sound Recording Films) in order to generate desired sharp images for the sound recording and minimize background noise generated by relatively high minimum densities typically associated with relatively fast camera negative origination films. Exposure of the optical soundtrack negative is conventionally performed in response to sound information recorded in a master magnetic sound tape (which may comprise a compilation of original audio, dubbing, music, sound effects, etc.).
The above discussion of sound and image synchronization primarily relates to conventional practice associated with production of a final print film designed for projection in a theater. Such production typically involves extensive editing procedures involving both images and sound, in addition to synchronization of the final edited images and sound track. When a motion picture film director desires to periodically check the quality of work then being filmed, he may rely on viewing print film images (commonly known as "dailies") or telecine transfer images made from rolls of origination film shot in the previous day. While it may be useful to provide original audio (e.g., actual original dialogue of actors in a scene) with a daily print to aid in evaluation of the work, dailies must be quickly prepared, and providing audio information in the form of an optical soundtrack would be inconvenient and costly as it would require the generation of a separate sound negative film recording and synchronized printing thereof on the print dailies as discussed above. Dailies accordingly do not typically include integral audio information, but rather conventionally are viewed as silent films. Various systems have been proposed for providing playback of audio or other information associated with a scene recorded on separate media during viewing of a print of the scene (including U.S. Pat. Nos. 4,893,921, 5,557,423, and WO 90/15361), but such systems invariably require a separate timing code or synchronization feature which adds to the complexity and costs of such systems. Even if original audio information were available for presentation with dailies in accordance with such systems, there would still be the requirement of aligning and synchronizing separate source media each time a daily print was to be viewed, which would lead to possible complexities and errors.
The use of magnetic recording stripes or layers in photographic elements has been previously disclosed. An innovation in data communication between different stages of film use and processing for motion picture film was introduced as described in the publication "DATAKODE Magnetic Control Surface" by Eastman Kodak Company 1983 (Publication No. V3-517). A layer approximately 5 .mu.m thick containing magnetic oxide particles was coated across the entire back surface of a roll of motion picture film to provide the capability to magnetically record digital data on the film without interfering with normal photographic use of the film. It has been suggested that this permitted recording of different types of digital data at different stages of production of a motion picture which allowed for information exchange such as camera, lighting and filter data at the time of shooting to printer exposure control information in the laboratory to theater automation control signals during exhibition. The use of magnetic recording strips or layers on motion picture films for recording and playing back audio information has also been disclosed, such as in U.S. Pat. Nos. 4,003,743, 4,279,945, 4,341,855, 5,633,127. More recently, it has been proposed to employ a virtually transparent magnetic layer on still photography filmstrip to allow for magnetic recording of data in one or more longitudinal tracks associated with individual film image frames for information exchange purposes as part of the recently introduced Advanced Photo System. An example of such a system is described in commonly assigned U.S. Pat. No. 4,965,627 issued Oct. 23, 1990. In order to provide quick access to particular data at any stage of film use, related data is preferably grouped and recorded in specific predetermined tracks. Camera data is recorded in several dedicated longitudinal tracks located along the filmstrip edges. The data is preferably recorded in pulse position encoded form in order to be largely independent of film transport velocity. There has been no specific suggestion of a convenient method, however, to provide original audio soundtracks on motion picture print dailies prepared from origination motion picture negative films which may be easily used to provide a playback of original audio while viewing the dailies without the need for special synchronization procedures.
It is a general aim of the present invention to provide a convenient method for recording audio information directly onto a motion picture film during filming of a motion picture scene, and for playback of original audio information stored on a motion picture film during viewing of the recorded motion picture scene.